Fermented food jars keep cracking??

[ChickenChick46]

Temperature reached may be the same if they were baked in a 240 degree oven. But the changes in temperature would be faster in a dry oven.

That's very true. My brain doesn't like to work at 5:40 A.M., lol.

 

[The Yardbird Life]

Baking them is your issue. It has changed the temper of the glass. You can't treat canning jars as we would a Pyrex product. Very different properties at work in the heating and cooling process.

 

[Newbie102]

IDK, it still doesn’t really make sense. The jars are not warm to the touch or anything and the gases should be escaping fine. But that must be it.

 

[Mother of Chaos]

IDK, it still doesn’t really make sense. The jars are not warm to the touch or anything and the gases should be escaping fine. But that must be it.

They were weakened when they were baked. And now it takes very little to make them crack.

 

[U_Stormcrow]

Yup, the baking did it. The only jars I see crack that way are large pickle jars subjected to thermal shock (when I put hot tap water in a cold jar I just emptied). Fridge 34* (sometimes colder). Our tap water 122*. *Ping* with some frequency. Same location and shape - the complex curve of the bottom plus the lettering guarantees uneven heating/cooling - its their weak spot. The shoulders are similar, if not quite as bad.

Our Ball jars don't do it, they've been annealed around 800* then allowed to cool very slowly and can now take the stress of a 100* temp change. By baking, you've re-introduced thermal stresses thru uneven heating and cooling (not your fault - no home oven heats consistently). Then, when pressure builds in your jars, cracks propagate along the thermal stress lines.

Use mason jars that you didn't bake, coffee filters with a good rubberband keeps bad out while allowing fermentation gasses to escape.

Worth the (re)investment.